1. Field of the Invention
The present invention relates to a photodiode, and more particularly, to a waveguide PIN (p-type, intrinsic, n-type) photodiode.
2. Description of the Related Art
Photodiodes are essential parts in local area optical networks such as wavelength division multiplexing (WDM)-passive optical networks (PONs) and e-PONs. Research on optical communication technologies is being actively pursued and ultra-high technology optical communication is widely used for a long distance back-bone network. However, coaxial cables are used as the main communication means for local area access networks, i.e., data communication between a base station and a general household or an office.
Generally, since local area access networks have many users, it is estimated that a full range of good quality services will be available to users when optical communication technologies will be fully developed. The communication speed of the local area optical network is expected to reach several hundreds of MHz to several GHz (e.g., 1.25 or 2.5 GHz). The most actively investigated photodiodes are a high-speed PIN photodiode having a light-receiving bandwidth of 40 GHz or more and an avalanche photodiode having a high gain rate. On the other hand, a waveguide PIN photodiode having a low speed less than 5 GHz is still not available on the market due to high package costs and low demand.
It is expected that the demand for receivers will rapidly increase when the local area optical communication market is revitalized in the near future. Accordingly, it is certain that the demand for low-speed waveguide PIN photodiodes that can be used to manufacture inexpensive receivers for local area optical communication will also increase. In this regard, low-speed waveguide PIN photodiodes should have high responsivity, high coupling coefficient when coupled to a single-mode optical fiber, high alignment tolerance, and low package costs.